1. Field of the Invention
The present invention relates to a printing system for controlling a printer having multiple print heads for the printing of an image on a recording medium based upon the alignment condition of the print heads. More specifically, the present invention concerns a printing system in which it is determined whether the print heads are effectively aligned and in which one of multiple different printing schemes is selected based upon the alignment determination.
2. Description of the Related Art
A conventional multiple print head printer typically prints an image on a recording medium in response to commands and data received from a printer driver that is executed within a computer attached to the printer. The conventional printer prints the image on the recording medium by moving the print heads in lateral scans across the recording medium while the print heads print an image corresponding to the print data received from the printer driver. The manner in which the printer driver directs the print heads to scan the recording medium for printing depends upon several factors including the type of image being printed, the desired resolution, and the type of recording medium being used. For example, the printer driver may command the printer to print an image by scanning over the same scan line of the recording medium several times in succession in order to improve the image quality. In addition, the printer may be commanded by the printer driver to print the current scan line in one direction and then to print the next scan line in the other direction. Print head speed and print head nozzle selection can also be varied to achieve the desired printed image. Various combinations of the aforementioned printer control operations may be used to achieve the desired image quality according to the print modes and conditions related to a given print request.
When the print heads are not effectively aligned with respect to each other, or with respect to the printer, the quality and resolution of the printed image can be adversely affected. For this reason, some conventional printers provide an alignment process whereby the printer driver and the printer operate in a coordinated fashion to determine the degree of misalignment of the print heads, and to align the print heads if necessary. The alignment process is generally performed whenever it is determined that the print heads may be misaligned, because: (1) the user changed one or more ink cartridges in the printer; (2) a specified amount of time or number of print jobs has elapsed since the last time the alignment process was performed, (3) the printer detects that the print heads are misaligned, or (4) the user spontaneously chooses to perform the alignment process. If the printer driver determines that the print heads may be misaligned for reasons discussed above, among others, the printer driver notifies the user of the problem by a dialog box on the computer display. This dialog box is generally displayed when the user attempts to send a print request to the printer from an application being executed in the computer. If the user chooses to initiate the alignment process, it is presumed by the printer driver that the alignment process has aligned the print heads sufficiently upon completion.
A problem arises when the user chooses not to perform the alignment process after being prompted with a dialog box as described above. Heretofore, printer drivers have either: (1) allowed the user to attempt to print the image in the normal fashion, thereby risking a reduction in quality of the printed image; or (2) prevented the user from proceeding with the print request until the alignment process is performed. This arrangement is unsatisfactory because a print request that is processed by a printer with misaligned print heads may have reduced image quality and because a user may desire to send a print request to the printer without taking the time to perform the alignment process.
What is needed is a printer that can determine whether the print heads are effectively aligned and that can allow the user to obtain the best image quality possible when the printer driver determines that the print heads may be misaligned.
The present invention addresses the foregoing by providing a printing system whereby one of multiple different printing schemes is selected based upon a determination that the print heads are not effectively aligned, thereby maintaining image quality and resolution. As a result, the user is allowed to print a quality image after being prompted to perform the alignment process and deciding not to do so.
In particular, the present invention relates to a printer driver for execution within a computer attached to a printer having multiple heads whereby the printer driver determines whether the print heads may be misaligned because: (1) the user changed one or more ink cartridges in the printer; (2) a specified amount of time or number of print jobs has elapsed since the last time the alignment process was performed, or (3) the printer detects that the print heads are misaligned. When the user attempts to initiate a print request, the printer driver generates a dialog box on the computer display prompting the user to perform the alignment process.
If the user chooses to continue the print request without performing the alignment process, the printer driver instructs the printer to print the requested image by using only one of the print heads, thereby reducing the adverse effects caused by misalignment of the print heads with respect to each other. For example, if the printer contains two of the same type of print heads, then the first one is chosen for printing when the print heads are misaligned. If, however, the print heads are a combination of a color ink print head and a black ink print head, then the color ink print head is used for printing when the print heads are misaligned, unless the image to be printed requires only black ink in which case the black ink print head is used. In this manner, the printer avoids image overlap and blurring that is caused by printing with two print heads that are misaligned with respect to each other.
In a further aspect of the invention, the printer driver instructs the printer to print the requested image by laterally scanning the print heads in one direction only when the user has chosen to perform the alignment process after being prompted to do so. In this manner, the image quality is improved when printing without alignment because unilateral scanning of the print heads results in a higher quality printed image than bi-directional printing when the print heads are misaligned with respect to their properly aligned positions within the printer, respectively.
Thus, only one print head is utilized for scanning the recording medium in a single direction when printing without alignment, however, the other print control parameters provided to the printer by the printer driver generally remains the same. For example, a print request for printing a high resolution image on plain paper when the print heads are aligned would require the printer to scan both print heads in both directions, and to repeat the printing of each scan line twice. If the same print request is made when the print heads are misaligned, however, the printer would scan only print head number one in one direction only, but would still repeat the printing of each scan line twice.
In a preferred embodiment of the present invention, a print request is denied by the printer driver in the event that the requested print mode cannot be supported with only one print head when printing without alignment. For example, if the user initiates a print request for a photo-quality image and is then prompted by the printer driver to perform the alignment process, the print request will be cancelled by the printer driver if the user elects to forego the alignment process. This is because the printing of a photo-quality image requires the use of both print heads and therefore cannot be printed without alignment wherein only one print head is utilized.
As a result of the present invention, the user is allowed to proceed with a print request when the print heads may be in a misaligned state and the printer driver selects a printing scheme in such a situation whereby only one print head is utilized for scanning the recording medium in one direction only. This scheme results in improved quality of the printed image when the print heads are misaligned with respect to each other or with respect to the printer.